Mystery Plan: Plant used in beer makingt

By John Nelson

Thursday, October 17, 2013

John Nelson/USC Herbarium
The stems of this plant are tough, and scratchy, equipped with stiff hairs, that make climbing easier.

Now here’s a word that is a bit tricky. Like many other German nouns, it is actually a composite, in this case two words joined together. The first word means “pleasure” and the second word means “material,” in the sense of “stuff.” Now in this garden, pictured here at the Botanical Garden in Munich, they devoted a large section to economically useful plants, and in this particular subsection, to various plants useful as luxury items. The vine pictured here is definitely useful in this regard, especially around Oktoberfest time.

It is a perennial species that is extremely variable, native to various parts of the temperate northern hemisphere, growing wild in thickets. A number of different species have actually been recognized, and they are frequently difficult to tell apart. (There has even been a North American species described.) Botanists have been scratching their heads for a long time as to the proper relationships of this plant. It is often considered a close relative of marijuana, actually…and has also been allied to elms and stinging-nettles.

This plant is a twining vine, occurring as either male or female individuals (usually). The stems are tough, and scratchy, equipped with stiff hairs, that make climbing easier. The leaves are also quite scratchy and rough. They are rather handsome, long-stalked, dark green and deeply lobed. Female plants produce axillary clusters of tiny, nondescript flowers, and these are crowded together into tight, cone-like affairs, featuring a number of overlapping bracts. The male plants don’t seem to be worth much, except for providing pollen, which is important. It’s the female flowers, though, when fully mature, that are of economic interest here.

The bracts of the female flower spikes are heavily invested with a variety of bitter-tasting compounds, mostly isolated in tiny glands on the bract surfaces. The ripe “cones” look a bit like a slightly elongated Brussels’ sprout. When dried and properly cured, they are aromatic and resinous, and of course used in the process of beer-making. It’s quite a complicated process, and an old one: this species has been cultivated for well over a thousand years. The compounds added to the malt impart stability and a delicate bitterness, and also tend to do away with bacteria, while leaving the friendly yeast alone. So, the plant doesn’t have anything to do with fermentation, but it’s extremely important in the modern brewing industry. That’s why they’re growing it in the “Genußmittel” part of the garden. Prost!

Answer: “Hops,” Humulus lupulus]

John Nelson is the curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications.

For more information, visit www.herbarium.org or call 803-777-8196, or email nelson@ sc.edu.

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